Ever since TechShop Portland went under one of the things that you found was really useful was a laser cutter. We had two different ones. An Epilog Helix 45W machine and a Chinese built Rabbit with a 80 watt laser. The chinese made machine was actually pretty good. Not as polished as the Epilog but in some ways was actually superior.

So I decided to build one. Not going to start from scratch though. At my friends surplus store two Hamilton Starlet Microlab fluid handling robots showed up. Its kind of a light duty gantry robot that can do repetitive tasks. A company that builds electron microscopes and FIB machines had bought these to try and automate loading wafers into a SEM. Didnt work out. So they are basically brand new. Here is a video of one:

He had it for a couple months and there was zero interest in it. The software is proprietary and you have to go to them to take a class before they will even sell you the software. Even the company that made it would only offer a pittance for it. The other day it hit me that it would be perfect for a laser cutter. Its completely servo driven. Maxon motors throughout. Rexroth slides on the Y and Z axis and THK on the X. Travel in X and Y is a little more than 36" x24"

The Y and Z axis. The Y uses a little pancake style brushless motor from Maxon. 30W, 40v or so. It is coupled to a spinning nut that drives it along the leadscrew. The lead screw looks to be 7 starts, 1/2" per turn, 1/4" teflon coated.

I got a couple servo drives off ebay. They are made by Elmo. Pretty neat little drive, they will run either brushed or brushless motors and you can control them with step and direction pulse inputs in positioning mode. They also have dual loop support so you can have a encoder on the motor and a linear encoder on the axis.

Last edited by macona on Sun Jan 30, 2011 9:02 am, edited 1 time in total.

I owned a lot of the equipment at TechShop so it mostly came home. The stuff that TechShop actually owned was auctioned off a couple weeks ago. A friend picked up the 80W Rabbit 12090 for $2200.

The servo drives showed up last week and I am now trying to figure out just how I want to do this. I had though of making a lifting table for the Z axis but now I am thinking of just putting the optics on the existing Z axis on the gantry. My only worry is the little Y axis motor will not have enough oomph, its only 30W. Ill just keep things light and see what happens. I can always throw in a small DC PM motor if I am not happy.

One thing of note. I will never use Steppers again if I dont have to. The price of PM servo drives has dropped to a point where they are completely in line with steppers. The drives from http://cncdrive.com are a good example.

Also trying to figure out what I want for a controller. The Rabbit we had used the MPC6515. It was not that bad but the software sucked eggs. There were always little issues in importing files. Once you got it in it was pretty decent and had a few advantages over the epilog software. But I am mostly looking at the controller from Full Spectrum. That looks right now to have the most promise. Though I have been around the block with new hardware that never lived up to expectations (Gecko G100, SmoothStepper).

I am probably going to install a 40W tube in the top of the machine and wrap the beam along the outside to the gantry. Since I believe the length of the tube is longer than the longest dimension of the enclosure I will probably have to install it diagonally. I have a bunch of kinematic mirror mounts lying around waiting for something like this and some real light ones that will be perfect for the flying head.

I think the next thing I really need to do is sit down and lay out boards that breakout the 30 pin flat cables that it uses to get power to the X axis encoder and up to the gantry. Also need to find a source of the FFC cables, 1mm pitch, 8 conductor, 40" Long.

Heres a pic of some of the controls. The two servo drives, Fuse holders, SSR and timer for the exhaust fan and some auxiliary relays.

Getting some things slowly sorted out. I got some silicone rubber insulated high flex wires that will feed the Z axis and Y axis motors and encoders. They have micro D connectors on the end but I can work with that. I have a couple spare cable sets so I can use one for the connectors on the end. Lucky for me the cables have one female and one male. Otherwise I would have to replace the connectors are these guys are almost $100 each!

I got the encoder for the Y axis today. Heidenhain LS403 series scale and reader. This is an exposed scale so there will be no friction resistance like the normal enclosed glass scales. That little motor is going to need all the help it can get. The scale outputs a 1v peak to peak quadrature sinusoidal analog signal. I happen to have one of the Heidenhain sine to ttl interpolator boards which converts the signal to something I can use. I am not sure what the multiplication factor is with the board I have, guess I will find out! The sensor head also has magnetic limit switches built in which is pretty cool. The scales are used. Hoping one is still good. The encoder strips mount in an aluminum rail that is glued to the machine. This allows removal for replacement or cleaning. Heres the data sheet on the linear encoders:

The main board breaks out the two 30 pin FFCs coming from the gantry and utilizes the existing linear encoder on the X axis. It also has a relay that will kill motor power to the servos in an estop condition and also can either kill power to the laser power supply or drop the enable line. The board uses mostly .1 spaced connectors except for a couple phoenix style connectors on the higher power section. The board is also meant to support different encoders for the Y axis with connection for an interpolation unit. Jumpers will bypass those connectors if it is not needed. The board is 4"x4"

The arm board takes the two 30 pin cable and breaks them out to two 16pin IDC right angle connectors. One for the Y encoder and one for the Y motor, Z mot, Z enc, and limits. The connection for Y motor and halls are grouped in the connector in case a fixed Y motor is mounted to the gantry itself. There is also a 8 pin FFC connector for the light bar that is on the machine already. The board is 1.77x 4"

The shuttle board has the DB-15 for the heidenhain encoders I have. Also a 8 pin connector for other encoders. Connectors with power for Y and Z homes are there. as well as a spare connector if we want to replace that little brushless motor with a brushed type. Also a connector for the existing maxon motor on the Z axis. Board is 2x2.5"

Got the boards mostly finished today. Looks like its time to start putting things together.

Big board is the main interface board. It connects the servo drives to the motors. The gantry is connected by Flexible Flat Cables which connect at the top right. This connects power, motor power, limits, and encoder feedback. The board on the left is where the FFC's terminate in the X Axis arm. From here they go to High flex silicone cables to connect the arm to the Y axis arm through the two 16pin IDC headers. They connect the Z axis motor and encoder and the Y axis encoder which are both mounted to the Y axis connecting to the Small board on top. There the heidenhain linear encoder plugs into the DB15, limits to the two white connectors and the Z motor to the little 6 pin IDC header.

The extra pads on the boards are for options like a different type of encoder on the Y axis or moving the Y axis motor to the side of the machine.

The main board also handles the estop and power distribution. The big relay cuts power to the laser power supply and the +40v main buss to the servo drives in the eventof an estop condition.